Shaft installation for processing of fuel-containing solid materials

ABSTRACT

A shaft kiln installation is used to burn pellets of solid materials containing volatile and/or solid fuels and at the same time to calcinate minerals. For this purpose, the installation uses in the heating, degassing (1,04) and combustion zones (1,06) a co-current flow of combustion gas. The installation has at least one first upper section (1,04;1,06) for carrying out the above-mentioned process steps. If necessary, a third counter-current cooling section (1,10) for the combustion material and a second, midddle section (1.08) that acts as a neutral zone, may be added. The heat content of the combustion gas and cooling air may be used for heating the combustion air.

The invention relates to a shaft installation, in particular to a shaftkiln, for processing of fuel-containing pieces of solid material bymeans of burning the same with air or oxygen-containing gas and/or forthe thermal treatment of mineral raw materials by means of burningpieces of fuel containing volatile components, with charging and removaldevices.

The invention also relates to a method for the processing offuel-containing pieces of solid materials in such a shaft installation.

A number of installations have been proposed for the processing offuel-containing pieces of solid materials and/or for the thermaltreatment of mineral raw materials by means of burning of pieces of fuelcontaining volatile components: tunnel furnaces, ring shaft kilns orinstallations, parallel-flow shaft kilns and co-current shaft kilns.

In the tunnel furnace the material to be treated is transported on carsthrough the furnace and is heated in the counter current. Because suchraw material is always very heterogenous in its composition and the sizedistribution of its grains, the optimal treatment temperature for theindividual pieces of the raw material varies. Because of this anddepending on the composition of the material, insufficient or excessivecombustion occurs which, in turn, can lead to caking of the material.However, this does not pose a problem in a tunnel furnace because thematerial is at rest and possible caking can therefore be broken up afterpassing through the furnace. But a considerable increase in cost isrequired because of this. However, the important disadvantage in the useof the tunnel furnace is that no flow through the material itself takesplace. Therefore the time for the gas extraction or gasification of thefuel bound in the material is very long and investment costs arecorrespondingly high.

For an economical solution, i.e. high daily tonnage output in whichflow-through of the material takes place, it is required that a reactordo not have any internal components.

These prerequisites are also fulfilled by a ring shaft installation witha plurality of kilns disposed in series, which operates on the kilnprinciple, which has proven itself in connection with such treatment.The ring conduits required for such a ring kiln process must be providedaltogether five times, namely for the pre-heated air, the cold air, thewaste gas, the ignition air and the pre-heat exhaust air. Thecorresponding difficulties and operational uncertainties are obvious.The individual kilns are filled with or emptied of solid material bysteps.

In DE-A1 3 310 495, a parallel-flow shaft kiln for the processing ortreatment of such solid materials is described and claimed. Reference ismade here also to the publications in GLUECKAUF 118, No. 21, p. 1098A,cited in this patent application.

The installation in accordance with the cited German laid-open patentapplication is used for the extraction of building materials or ofaggregates for the same from hard coal dressing wastes. For this purposethese are separated by grain size, dried and preheated in a firstprocess step, heated and brought to reaction in a second process stepand maintained at a set temperature in a third process step. Theinstallation comprises chambers disposed concentrically to each other, adrying and preheating chamber being surrounded by a heating and reactionchamber. Below the heating and reaction chamber is located a loiteringchamber from which the treated material reaches the outlet chamber of akiln which also surrounds the loitering chamber. The gases freed duringthe heating and reaction of the treated material are routed to acombustion chamber disposed in a conical clearance surrounded by thekiln.

DE-A1 3 509 275 describes and claims a method for the thermal treatmentof coal dressing wastes in at least two separate treatment steps, thewastes being dried in a first step and heated in a second step andsubsequently cooled in a cooling step. The tailings are dried underconstant agitation directly in the counter current by air indirectlyheated in the cooling step or by other heated carrier gases and arepreheated to a temperature of the solid material of up to 200° C. andare then heated directly and/or indirectly to a final temperature ofbetween 750° to 950° C. in the steps following the drying step. Theheating gases consist of extraction gases partially circulated and ofcombustion gases.

Finally, the object of EP-A1 0 059 542 relates to a shaft combustioninstallation for the calcination of minerals and/or the burning of solidfuels, if need be waste materials. Among others, cooling air directlyfrom the lower part of the furnace is always used, this air beingintroduced into the furnace under pressure and through complexdistribution installations.

In contrast thereto this invention relates to a single shaft kilnthrough which solid material as well as air or gas are continuously fed,namely in the preheating, gas extraction and combustion zones essentialfor the treatment or processing of the material, in co-current and, ifneed be only in the cooling zone in counter current. The neutral zoneprovided therebetween is used, among others, for the thermal treatmentof the material. By means of these novel arrangements in the totalinstallation, i.e. by means of this novel execution of the process, anoptimal matching of the kinetics of the reactions taking place in theshaft kiln with the corresponding thermodynamic balances is achieved:because of the heat recuperation in the cooling zone the energy balanceof the installation is favorable. Above all, however, it is attainedthat all volatile combustible components are surely routed to thecombustion zone and burned there with few pollutants.

In particular the shaft installation in accordance with the inventionpermits the use of only the heat contents of the combustion and coolingair in the air utilized. This is the most important prerequisite for acombined utilization for calcination and for the combustion of wastematerials. Also, slight underpressure can be used at the shaft kilninlet, in the solid material feed area as well as in the air supply,which considerably simplifies the construction of the installation. Forthe reasons cited, air distribution at the inlet poses no particularproblems.

Also, the shaft installation in accordance with the invention issuitable for the use of naturally occuring or processed or preparedwaste materials of every kind.

In U.S. patent application Ser. No. 023 800 a group of such solid fuelsmade of processed waste materials is described; the fuels in the form ofbriquets have a fuel component, a neutralizing component and a wastematerial component. The latter can be a liquid. Preferred fuelcompositions are those which have a total of no more than 40% by weightof liquid and a gross calorific value of at least 450 kJ/kg. These fuelbriquets are formed under pressure and are burned at temperatures above1,150° C.

The shaft installation in accordance with the invention for theprocessing of fuel-containing pieces of solid material by means ofburning the same with air or oxygen-containing gas and/or for thethermal treatment of mineral raw materials by means of burning pieces offuel containing volatile components, with chargng and removal devices,is characterized by a first upper shaft segment for preheating, gasextraction and combustion zones with the combustion air inlet, in thedirection of flow, upstream of the preheating zone and the waste airoutlet downstream of the combustion zone so that in this segment thesolid material and the gas are routed co-currently, by either a hotdischarge with a separate component for the subsequent cooling of thematerial or by a third lower shaft segment for the cooling zone with thecooling air supply behind and the cooling air exhaust ahead of thecooling zone so that in this segment the solid material and the gas arerouted counter-currently and a second, middle segment for a neutral zonewith the waste gas exhaust ahead of and the cooling air exhaust behindthe neutral zone.

If required, the recited shaft installation has devices for the indirectuse of the heated cooling air; also, devices for the exhaust of thewaste gases at the end of the combustion zone and for the routing ofthese combustion gases to a heat exchanger and/or a waste gas scrubbermay be provided.

Temperature and pressure measuring instruments are advantageouslydisposed in the waste gas and cooling air exhausts for monitoring theprocess.

If required, internal components, for example guide panels, may beprovided in the shaft installation recited above; they are used forconducting the heat from the combustion zone to the preheating zone.

The method in accordance with the invention is used for the processingof fuel-containing pieces of solid material by means of burning the samewith air or oxygen-containing gas in a shaft installation and ischaracterized by method steps in the following order:

Heating, gas extraction and burning of the solid fuel in a co-currentwith air or oxygen-containing gas for reaching a preselectedtemperature, by maintaining the material to burned at the saidtemperature and by cooling the material to be burned by air oroxygen-containing gas in counter current, control of the process takingplace by means of the temperature of the combustion air or by means ofthe addition of inert materials to the material fed in.

Among others, the shaft installation is used for processing of coaldressing wastes. However, other specific uses are conceivable in thespirit of the method according to the invention.

The installation in accordance with the invention will now be describedby means of an exemplary embodiment. The attached FIGS. 1 and 2 are usedfor this. This description also includes the method according to theinvention.

The installation shown is the shaft kiln having all three segments.

FIGS. 1 and 2 show the installation according to the invention purelyschematically:

FIG. 2 shows the shaft kiln per se; in it the reference numerals mean

    ______________________________________                                        1.01            charging silo,                                                1.02            double lock mouth,                                            1.03            combustion air inlet,                                         1.04            preheating zone,                                              1.05            combustion front,                                             1.06            combustion zone,                                              1.07            waste gas exhaust,                                            1.08            neutral zone,                                                 1.09            cooling air exhaust,                                          1.10            cooling zone,                                                 1.11            discharge plate,                                              1.12            cooling air inlet, and                                        1.13            double lock discharge.                                        ______________________________________                                    

FIG. 2 is a preferred embodiment of the total shaft installation, in itthe reference numerals mean______________________________________2.01cooling air exhaust,2.02 cooling air heat exchanger,2.03 conveyorblower,2.04 combustion air inlet,2.05 combustion gas exhaust,2.06 SO₂filter,2.07 waste gas heat exchanger,2.08 HF-filter,2.09 dust anddroplet filter and2.10 exhaustfan.______________________________________

DECLARATION CITED IN ARTICLE 19

The present patent application is limited to the embodiment inaccordance with original FIG. 2, used for the processing of waste fueland for the thermal treatment of mineral raw materials.

In connection with this, in the national phases

the teachings of the two publications relevant to the inventionaccording to the International Search Report and their combination willbe extensively cited and

the abstract will be changed accordingly.

The object of EP-A1 0 059 542 relates to a shaft combustion installationfor the calcination of minerals and/or the burning of solid fuels, ifneed be waste materials. Among others, cooling air directly from thelower part of the furnace is always used, this air being introduced intothe furnace under pressure and through complex distributioninstallations. Such cooling air, however, is never completely free ofharmful combustion products, because the material to be burned is stillat its highest temperature at the beginning of the cooling segment andthere comes into contact with the hot cooling air. In the processharmful volatile combustion products are discharged into the air.

Since these harmful substances are circulated in the installation inaccordance with EP-A1 0 059 542, the system automatically attains ahigher level of harmful substances which is not acceptable duringcalcination of most mineral materials.

The installation in accordance with the cited EP-A2-0 120 486 is usedfor obtaining building materials or of aggregates for the same from hardcoal dressing wastes. For this purpose these are separated from grainsize, dried and preheated in a first process step, heated and brought toreaction in a second process step and maintained at a set temperature ina third process step. The installation comprises chambers disposedconcentrically to each other and having diameters variable in height, adrying and preheating chamber being surrounded by a heating and reactionchamber. Below the heating and reaction chamber is located a loiteringchamber from which the treated material reaches the outlet chamber of akiln which also surrounds the loitering chamber.

The gasses freed during the heating and reaction of the treated materialare routed to a combustion chamber disposed in a conical clearancesurrounded by the kiln. Subsequently the combustion gases can come intodirect contact with the material to be burned.

Neither the method nor the device in accordance with EP-A-2-0 120 486are described as at all suitable for calcination of minerals--inparticular not if waste fuel materials are used. Neither does acombination of the teachings of the two EP references just discussedlead to the solution in accordance with the invention. The object of theinvention alone--a method as well as an installation for the utilizationof low-grade fuels, including waste fuel materials, as well as thelow-contamination calcination of minerals with use of the citedfuels--and even more so the attainment of this object according to theinvention with the method and the shaft kiln installation in which thecooling air is used only for the heating of combustion air and thecombustion gases are used after heat exchange and expensivescrubbing--only for fuel utilization!--, cannot be found in the combinedteachings cited.

What is claimed is:
 1. A shaft installation having a vertical shafthaving a plurality of sections in series including a preheating section,a combustion section, a neutral section, and a cooling sectioncomprising:(a) a charging means at the top of said furnace through whichsolid materials containing volatile components used as fuel are fed in adownward direction; (b) gas inlet means near the top of said furnace forintroducing combustion gas which flows downwardly and concurrently withthe solid materials in an upper preheating section where the solidmaterial is partially combusted and then through the combustion sectionwhere the solid material is completely combusted; (c) gas outlet meansat the lower end of the combustion section for removing product gasesformed in the preheating and combustion sections from the furnace, (d) aneutral section of said furnace wherein the combusted solids flowdownwardly into the top of the cooling section; (e) second gas outletmeans at the top of said cooling section for removing cooling gases fromthe cooling section and the furnace; (f) a cooling section where thedownwardly moving solids flow counter-current to upwardly flowingcooling gas introduced into the furnace through second gas inlet meansat the bottom of the cooling section and the furnace.
 2. A shaftinstallation in accordance with claim 1, which further comprises a heatexchange means where the heated cooling gas removed from the second gasoutlet of the furnace is passed in heat exchange relationship with thecombustion gas being introduced into the furnace through the first gasinlet means.
 3. A shaft installation in accordance with claim 1 or 2,which further comprises devices which connect said waste gases removedfrom the furnace through the first gas outlet means to a heat exchangerinstallation, a waste gas scrubbing installation or both.
 4. A shaftinstallation in accordance with claim 1, which further comprisestemperature and pressure measuring devices disposed in the waste gas andcooling air exhausts removed from the first and second gas outlet means,respectively.
 5. A method for the processing of solid materialscontaining volatile components as a fuel in which the material is fedinto the top of the shaft furnace through a feeder and descends bygravity through a plurality of zones in series including an upperpre-heating zone, a combustion zone, a neutral or quiescent zone, and acooling zone comprising the steps of:(a) feeding the materialconcurrently with a combustion gas comprising air or anoxygen-containing gas introduced at the top of said furnace to pre-heatthe material and partially combust said feed material to product gas,(b) passing downwardly and concurrently said feed material, saidcombustion gas, and said product gas into said combustion zone andtherein heating the partially combusted material obtained in step (a) todry and vaporize said solid material and a produce additional combustionproduct gases, (c) removing said product gases formed in step (a) and(b) from the shaft furnace near the bottom of said combustion zone forfurther recovery, (d) flowing the solid material freed of product gasesin step (c) through said neutral zone, (e) allowing said solid materialfrom step (d) to move downwardly through a cooling zone countercurrentto a cooling gas introduced at a lower end of said shaft furnace andremoved from the furnace between the bottom of the neutral zone and topof the cooling zone, and (f) removing cooled residual solid materialfrom the bottom of the furnace.